Connection Reset & CPU Usage

Hi,

Im creating an e-learning platform using WordPress. When i do simple things like navigate through admin panel, write a new blog post etc. i usually face with “Connection Reset” page, maybe the reason is CPU usage.

My hosting provider is Natro.com (Im using business plan, this host is based in my country, also they have increased the in server limits and they are saying me that my problem is not releated with them.). I analyzed CPU usage of plugins, %46 of the usage was from Yoast SEO, but i cant remove it since SEO is a crucial factor me.

My website optimization is still in WIP but now i get %81 from GTMetrix.

My Theme: Goodlayers – Clever
My Plugins:
WP Super Cache
WP-Optimize
Wordfence Security
WP-Mail-SMTP
Prevent Concurrent Logins
Goodlayers LMS
Goodlayers Shortcode
Master Slider Pro
Yoast SEO
The Things I Have Tried:
1- Compress images.
2- Minify CSS & Js.
3- Clean & optimize database.
4- GZip compression.
5- Disable WP-Cron.
6- Remove unnecessary plugins.
7- Install cache plugin. (It is not working for me, i still get “Leverage browser caching” problem from GTMatrix)

EDIT: Installed WP Fastest Cache and it increased my GTMetrix score to %98! Ill check if the problems are fixed or not.